The invention concerns a transporting roller for advancing workpieces made of wood, plastic, and the like and provided with teeth arranged in distribution about the circumference.
Such transporting rollers are used, for example, in woodworking machines and serve for transporting the pieces of wood to be machined on a support table in this machine. The transporting rollers are pressed with a roller pressure against the pieces of wood to be transported and are driven in rotation. The teeth engage the topside of the pieces of wood and impart to them an advancing force upon rotation.
In known transporting rollers (EP 0 273 172 B1), the teeth are provided with contact surfaces extending transversely to their flank and limiting the penetration depth of the teeth into the workpiece. The number of teeth that penetrate simultaneously into the workpiece, or contact it, depends on the diameter of the transporting roller and the roller pressure. Due to wear, the pointed teeth however become rounded, do not penetrate as easily into the workpiece, and reduce therefore the advancing action. Accordingly, it is necessary to press the transporting roller with greater force onto the workpieces in order to obtain the same advancing effect. In case of abrasive workpieces or abrasive pieces of wood or a long duration of use, the teeth will wear to such an extent that the force transmission from the transporting roller onto the workpiece is achieved only by the contact surfaces. The effect of the transporting roller is thus greatly reduced and can be compensated only, at least partially, by high roller pressure. Higher roller pressures effect greater friction forces on the surface of the workpieces contacting the support table which counteract the advancing direction and advancing force. The wear of the teeth limits thus the service life and duration of use of the transporting roller.
A further aspect is soiling of the transporting roller by resin deposits or by wood chips or splinters that are produced upon penetration into the workpiece. Strongly soiled transporting rollers also cannot penetrate as far and as easily into the workpiece so that the advancing force is reduced.
It is an object of the invention to configure a transporting roller of the aforementioned kind in such a way that with it a high advancing force is achieved with only minimal roller pressure over an extended duration of use and service life of the transporting roller.